1. Field of the Invention
This invention relates generally to trocars and obturators and more specifically to devices for shielding the sharp tip of an obturator.
2. Discussion of the Prior Art
Mechanical trocars typically include a cannula defining a working channel and a housing for seals which inhibit the escape of insufflation gasses. The cannula of the trocar is adapted to be positioned across the abdominal wall of a patient using an obturator which is initially inserted into the working channel and then removed once the cannula is in place. This obturator is provided with a sharp distal tip which facilitates the puncture of the abdominal wall and permits the cannula to be moved into position through the resulting hole.
When the obturator is initially inserted into the cannula, it must pass through the seal mechanism at the proximal end of the working channel. If this sharp tip is not shielded, it can cut or otherwise damage the seals in the housing.
In the past, shields have been biased to a forward position covering the sharp tip during preliminary insertion of the obturator. As the tip and shield are moved against the abdominal wall, the sharp tip moves forward while the shield is forced rearwardly of the tip. As the hole is punched through the abdomen, the shield is free to follow its bias in the distal direction eventually covering the tip. This is a very complex mechanism and greatly increases the cost of manufacture. It also relies upon the abdominal wall and the surgeon to force the shield in the proximal direction in order to expose the tip. The magnitude of the required force is significant and must be continuously exerted on the shield during the puncture process.